Polyurethane (PU) is one of the six most important synthetic materials and widely used in the fields of buildings with energy conservation, transportation industry including auto, metro or high-speed rail and new energy. Recently, research on flame retardancy of rigid polyurethane foam is paid much attention because of serious fire accidents. Therefore, it is of great urgency to improve the flame class of rigid polyurethane foam without obviously subdued effect on other performance.
Chinese patent application No. CN101962474A discloses a kind of environment-friendly and high flame retardancy rigid polyurethane foam produced by reaction among polyether polyol, pentane, flame retardant, modified hollow microsphere and polyisocyanate in the presence of foam stabilizer and/or catalyst, which is well used for heat preservation of building exterior, plumbing and refrigerating apparatus as vertical combustion meeting the requirement of V-0 grade. Another Chinese patent application No. CN102875762A discloses a kind of high flame retardancy rigid polyurethane foam using composited flame retardant with the limiting oxygen index value being over 30. This kind of rigid polyurethane foam has high flame retardancy, low smokiness and high fireproof heat insulation, which is safe to use. It can be seen that the existing flame-retardant technology of rigid polyurethane foam is focused on adding flame retardant, which is of low cost, quick recycling and great promising application.
However, the adding-type flame-retardant technology has some problems: (1) high adding amount of flame retardant for reaching a certain of desirable flame retard effect; (2) poor compatibility with polyurethane matrix with the result that additive may migrate to the surface of material.